By Zach Friend, Supervisor, Second District
Anyone who lives in the Rio Del Mar flats area, or has driven there in the winter, knows that large sections are susceptible to flooding and even become impassible.
Recently, the County held an outreach meeting with residents in the Rio Del Mar flats area to discuss some of the major progress that has occurred in the last year on bringing this long-needed drainage project to fruition and provide an overview of the drainage district needed for ongoing maintenance.
Why Does It Flood?
The area floods due to the development occurring on a historic floodplain and the current drainage system’s inability to drain to Aptos Creek when the river levels are high.
A photo taken from inside a vehicle shows Aptos Beach Drive starting to flood winter 2019. • Photo Credit: Steven Allen
As those that live in the area are acutely aware, the most frequent flooding problem is significant ponding during rainfall-runoff events. This ponding can occur multiple times each year even during relatively normal rainfall events.
With frequent events, such as a 2-year rainfall event, more ponding depths become sufficient for building damage. Road deterioration is also exacerbated by the standing water.
Public Works has noted that the ponding occurs because the existing gravity-flow stormwater drainage system has inadequate conveyance, due to the neighborhood’s topography (gentle sloping) which results in low flow velocities.
Additionally, the situation is also made worse from sediment and vegetative debris accumulation in the pipes. The flooding is generally concentrated along Aptos Beach Drive, the adjacent side streets, and the Esplanade, which are the lowest areas in the Flats neighborhood.
What Is Proposed?
County Public Works used a grant from FEMA to explore solutions to these flooding and drainage issues. The proposed design will install drainage improvements consisting of new and replacement underground storm drains, installation of a new pump station and relocate stormwater outfall to a new location to alleviate flooding and also improve the water quality that runs off.
The project will reduce flooding and emergency response during flooding events while reducing pollution discharges to the creek where fish habitat and water quality are a concern. The project is designed for 10-year flood events.
The new stormwater pump station will significantly increase the conveyance capacity of the stormwater drainage system while the new gravity-flow pipe will intercept runoff flowing down the hill into the flats at an elevation above the flats — reducing runoff volume into the neighborhood.
The estimated construction cost for the project is $4,802,704, and late last summer Public Works received $4,204,588 in grant funding from three agencies to help pay for the project including FEMA, Cal OES and the California Department of Water Resources through the Integrated Regional Water Management program.
The remaining local matching funds will come from the limited drainage impact fees the County has on hand. This state and federal funding (and local match) covers the construction.
However, no grant funding is available for ongoing operations and maintenance.
Once the project is constructed, the pumps and infiltration pits will require annual maintenance, which is currently estimated at approximately $121,000 per year. Currently, there is not a funding source for the ongoing maintenance and the project will need annual maintenance funding to move forward (or the construction grant funds will need to be returned).
As part of the community meeting, Public Works discussed the creation of a benefit assessment area in the flats to fund the ongoing maintenance. The formation would be compliant with Proposition 218, which requires the assessment to coincide with those receiving direct benefits. It requires a vote of the property owners that would be part of the assessment district.
Each property owner (residential, commercial and even the public property that the County and State owns) would be provided a ballot for consideration of formation of the district. If approved, this would provide the ongoing maintenance costs and the project could move forward.
The County has a page with information about the flood mitigation proposal where you can look at the proposed benefit assessment area, ask questions, look at answers to questions others have asked, see the proposed assessment for each parcel and more. That website is: www.civicmic.com/county-of-santa-cruz/
The goal is to have the ballots sent in July and, if approved, construction would follow (construction is expected to take approximately seven months).
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As always, I appreciate any feedback you may have on this (or any other County issue). I’m maintaining regular updates on social media at www.facebook.com/supervisorfriend you can always call me at 454-2200.